We also made a bunch of other structural and floor plan changes.

However, THE only bathroom is on the first floor beside the kitchen and back door.

AC units do tend to walk away from vacant C class houses in Indy which is why all of mine are installed on a concrete pad and chained down.

how far did the concrete get down the pipes?

The numbers are not bad but I have no idea what the cost of doing paint, new flooring, bathrooms, kitchens etc.

I'm specifically looking at renovating the kitchen, bathroom, floors, and basement flooring. 

Full repaint, brand new LVP flooring and carpet throughout the home.

Houses were built of a lot more concrete, but I'm thinking if there was a fire, your house would burn down. 

Repurposing each floor into spacious home suites, with indoor gardens in each home, a restaurant on an entire floor, the rooftop with a pool and gym...capital heavy but if it can be streamlined into a science, maybe its new upscale housing fir the cost of a complete interior remodel vs building a stick frame on new land out farther away from the city.

It's a 5 bedroom apartment, 3rd floor unit.